The present invention relates to a method and an apparatus for reclaiming deicer from produced water of an oil well and, in particular, methanol.
Oil or gas wells frequently produce a mixed stream of gas, liquid hydrocarbons and water. The mixed stream flows or is pumped to surface and separated. After recovery of the oil and/or gas, the produced water is reinjected into a disposal well.
In cold weather conditions, there is a danger of the mixed stream freezing or hydrating due to the presence of water. Freezing or hydrating can occur anywhere in the process before the water content is totally removed. In order to prevent freezing or hydrating, a deicer is injected into the mixed stream of oil and water. There are various substances suitable for use as deicer, methanol being one of the most common.
The water stream being injected into disposal wells at the present time can consist of as much as 90% methanol. It is theoretically possible to recover this methanol through a distillation process, however, this has not been done to date due to the high energy costs associated with such a distillation process.
What is required is a method and an apparatus for reclaiming deicer from produced water of an oil or gas well in a cost effective manner.
According to the present invention there is provided an apparatus for reclaiming deicer from produced water of an oil well which includes a fractionation tower having a top condenser section, a bottom heat exchanger section and an intermediate packing section. A condenser is positioned in the condenser section. A deicer outlet is positioned in the condenser section, for removal of condensed deicer. An inlet is provided to receive produced water contaminated by deicer. The inlet is coupled to the condenser section such that produced water must pass through the condenser to enter the inlet. A water outlet is provided in the heat exchanger section. Means is provided for controlling operation of the water outlet to maintain a predetermined level of accumulated water in the heat exchanger section. A heat exchanger positioned in the heat exchanger section. The heat exchanger is adapted to be coupled with a source of hot fluids produced by an external heat source. The circulation of hot fluids through the heat exchanger heats accumulated water in the heat exchanger section.
The recovery of deicer will always taken place after water contaminated by deicer has been separated from oil. The separation of water and oil is a process that requires a lot of energy, a large portion of which is currently wasted. The present apparatus is designed to run off excess heat generated during oil separation. This excess heat, in the form of hot fluids, is passed through the heat exchanger of the fractionation tower to heating costs. In order to condense the deicer after separation, the produced water stream is passed through the condenser prior to entering the fractionation tower through the inlet.